Anti-Staphylococcal Enterotoxinogenesis of Lactococcus lactis in Algerian Raw Milk Cheese

Staphylococcus aureus is a potential pathogen contaminating raw milk and dairy products, where it is able to produce thermostable enterotoxins that can cause staphylococcal food poisoning. This study was undertaken to investigate the inhibitory activity of a Lactococcus lactis strain (isolated from milk) on S. aureus growth and staphylococcal enterotoxin A (SEA) production. In the presence of L. lactis, the number of the pathogen decreased significantly (p<0.05) after 6 h of incubation in a laboratory medium and milk (3 log CFU/mL reduction compared to pure cultures). SEA concentration was reduced by 79% in the co-cultures. S. aureus was unable to reach population levels permitting SEA production in the cheese inoculated with L. lactis during 32 days of storage. In contrast, during the same period, it attained 7 log CFU/g in the cheese manufactured without the lactococcal strain, a level which permitted SEA detection in the cheese extracts. However, this enterotoxin was never detected in the cheese harbouring L. lactis. These results demonstrate the anti-staphylococcal enterotoxinogenesis potential of the L. lactis strain and its usefulness in raw milk cheese biopreservation.